Transesterification process for making trialiphatic phosphite esters



United States Patent ()fiiice 3,056,823 Patented Oct. 2, 1962 3,056,823 TRANSESTEICATIGN PRGCESS FGR MAKING TRIALEHATHC PHQFyPHHTE ESTERS Ingenuin Hechenbleikner, Ciarkshnrg, and Albro T. Gaul,

Adams, Mass, assignors, by mesne assignments, to Hooker Chemicai Corporation, Niagara Falls, N.Y., a corporation of New York No Drawing. Filed May 31, 1956, Ser. No. 588,218 22 Claims. (Cl. 260-461) The present invention relates to the preparation of trialiphatic hydrocarbon phosphites.

It is an object of the present invention to prepare trialiphatic hydrocarbon phosphites in a simpler and more economical fashion than has been possible in the past.

An additional object is to prepare trialkyl phosphites from triaryl phosphites in improved yields and with a corresponding reduction in byproducts.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

It has now been found that these objects can be attained by transesterifying a triaryl phosphite with a monohydroxy aliphatic hydrocarbon in the presence of a small but catalytically eifective amount of a metal alcoholate or metal phenolate.

As triaryl phosphites there can be employed triphenyl phosphite, tri p-cresyl phosphite, tri o-cresyl phosphite, tri m-cresyl phosphite, tri 2,4-xylenyl phosphite, tri butylphenyl phosphite and other tri alkylated aryl phosphites, tri o-chlorophenyl phosphite, tri p-chlorophenyl phosphite and tri m-chlorophenyl phosphite.

As monohydroxy aliphatic hydrocarbons there can be employed alkanols and alkenols, such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec. butyl alcohol, tert. butyl alcohol, isobutyl alcohol, amyl alcohol, hexyl alcohol, isoocetyl alcohol, Z-ethyl hexyl alcohol, n-octyl alcohol, nonyl alcohol, decyl alcohol, lauryl alcohol, cetyl alcohol, octadecenyl alcohol oleyl alcohol), butene 2-ol-1, etc. For highest yields the alkanol preferably has 6 carbon atoms or above and the alkenol is of even higher molecular weight.

As the metallic alcoholate or phenolate there preferably is employed the alkali metal salt of an alcohol or phenol. Typical examples are sodium methylate, lithium methylate, potassium methylate, sodium ethylate, sodium isopropylate, sodium dodecylate, sodium cetylate, sodium octadecylate, sodium phenolate, potassium phenolate, sodium cresylate, etc. There can also be used metal alcoholates such as calcium ethylate, etc.

To avoid contamination there is preferably employed the alcoholate of the particular alcohol which is to be transesterified with the triaryl phosphite or there is em ployed a phenolate. Instead of employing a preformed alcoholate, the alcoholate can be formed in situ by adding the metal, e.g., sodium, potassium or lithium to the alcohol, e.g., methanol, prior to adding the triaryl phosphite. The aliphatic mono alcohol and triaryl phosphite are reacted in the mol ratio of 3 mols of the alcohol to 1 mol of the triaryl phosphite. If less alcohol is used, then the yield of the desired trialkyl or trialkenyl phosphite is reduced and by-products are formed, such as monoalkyl diaryl phosphites and dialkyl monoaryl phosphites. Generally there is no advantage in using a large excess of the monohydric alcohol over the 3 mols as the excess alcohol must be recovered. Usually there is employed a slight excess of alcohol over that required to react with the metal when the alcoholate is formed in situ to insure complete reaction, although it is to be understood that there need be no excess of the alcohol over the 3 mols per mol of triaryl phosphite. Similarly, if the metal alcoholate or phenolate is preformed, there is no need to use an excess of the alcohol.

The metal alcoholate or phenolate is used in distinctly catalytic amounts, e.g., between 0.001 and 0.20 mol, preferably between 0.01 and 0.05 mol, per mol of triaryl phosphite.

it is known, Kosolapoff Organophosphorus Compounds, pages 191-192, to react triaryl phosphites with sodium alkoxide according to the equation:

Such a reaction, however, is distinct from that employed in the present invention as the alkoxide in the Kosolapoff reaction is employed as a reactant rather than as a catalyst. Furthermore, the amount of metal alcoholate employed as a catalyst in the present interchange of an alcohol with a triaryl phosphite is much less than molar amounts and still it is possible to obtain the formation of trialkyl phosphite in yields of or above with alkanols of 8 or more carbon atoms. This is surprising as in the absence of the metal alcohol or phenolate catalyst there is formed a mixture of monoalkyl diaryl phosphite and dialkyl monoaryl phosphite and very little trialkyl phosphite is formed, or phosphonates are formed, of. Kosolapolf. Yet, the addition of merely a small amount of the metal alcoholate or phenolate catalyst completely alters the reaction of the alcohol and aryl phosphite.

It is to be understood that the present invention is limited to preparing phosphites from monohydroxy aliphatic hydrocarbons. The problems attending such reactions are entirely dilferent from those in preparing phosphites from polyhydric alcohols, such as the glycols. Thus, the glycols, e.g., ethylene glycol, will react completely with triaryl phosphites, e.g., triphenyl phosphite, either without a catalyst or in the presence of either acidic or alkaline catalysts. In the case of the glycols, cyclic products are formed in contrast to the linear products obtained with alkanols and alkenols.

Additionally, the use of catalytic amounts of the metal alcoholate or phenolate appears to reduce both the time and temperature required for reaction. A further surprising factor in the present process is that the ester interchange goes a substantial way toward completion with alcohols having a boiling point below that of the phenol formed in the interchange. In fact, the reaction goes so rapidly that it is possible in many instances to immediately heat the mixture in order to remove the phenol formed by distillation, or, in the event that the trialkyl or trialkenyl phosphite is lower boiling than the phenol, to remove the phosphite formed. When the phosphite formed has a boiling point approximately the same as that of the phenol formed, instead of distillation, the phosphite and phenol can be separated by addition of aqueous alkali in an amount equivalent to the phenol in order to form an aqueous layer containing the phenol and an organic layer containing the trialkyl or trialkenyl phosphite.

The reaction can be carried out at room temperature or below or the mixture can be heated to remove the phenol or product, which ever is lower boiling. Thus, temperatures from 0 C. to C. can be employed. The pressure can be atmospheric, superatmospheric or subatmospheric. Preferably, the mixture of alcohol, catalyst and trialkyl phosphite is allowed to stand at room temperature and atmospheric pressure for 30 to 3 120 minutes, and then distillation is carried out at reduced pressure, preferably to 20 mm.

While only a single alkanol or alkenol is used, if a pure product is obtained, it is evident that mixed trialkyl phosphites can be obtained by employing a mixture of alcohols, e.g., monolauryl distearyl phosphite can be formed by employing 2 mols of stearyl alcohol, 1 mol of lauryl alcohol, 1 mol of triphenyl phosphite and 0.02 mol of sodium phenolate and heating the mixture at 10-20 mm. to remove the phenol formed.

The trialkyl and trialkenyl phosphites of the present invention can be used as stabilizers for vinyl chloride resins and as oxidation inhibitors for lubricating oils.

In the examples and elsewhere in the specification and claims, unless otherwise indicated, all parts and percentages are by weight.

Example 1 0.5 gram of metallic sodium was added to 229.4 grams (3.1 mols) of n-butanol. This formed the sodium butylate catalyst in situ. Then 310 grams (1.0 mol) of triphenyl phosphite was added. A moderate exotherrn occurred. After 10 minutes, the mixture was heated to 170 C. and no refluxing occurred, showing that very little of the n-butanol (B.P. 130 C.) remained. The mixture was then cooled to room temperature and washed with 3 mols of a 10% solution of sodium hydroxide. The aqueous layer was separated from the organic layer and the latter distilled at reduced pressure to yield 80% tributyl phosphite and 18% dibutyl phenyl phosphite based on the theoretical amount obtainable from the triphenyl phosphite starting material.

In a comparable example, when 3 mols of n-butanol were heated under reflux with triphenyl phosphite without the sodium butylate catalyst, reflux occurred 130 C. This shows that there was still substantial quantities of unreacted butanol. When the sodium butylate catalyst was used, however, there was no refluxing, even at 170 C., but instead the reaction went smoothly and was complete before the reaction mixture could be heated to the boiling point of butanol.

Example 2 The process described in Example 1 was repeated, but the 3.1 mols of n-butanol were replaced by 179.8 grams (3.1 mols) of allyl alcohol and 1.0 gram of sodium was employed. The organic product obtained was fractionally distilled at reduced pressure to give 65% triallyl phosphite and 20% diallyl phenyl phosphite based on the triphenyl phosphite starting material.

Example 3 0.5 gram of metallic sodium was added to 403 grams (3.1 mols) of 2-et-hyl hexanol. Then 1 mol of triphenyl phosphite was added, the mixture allowed to stand for 30 minutes and then the phenol formed was distilled off at 10-20 mm. pressure. The tri-2-ethylhexyl phosphite formed was recovered as a colorless liquid by distillation at 130-132 C. at 1 mm. pressure. The yield was 95% based on the triphenyl phosphite starting material.

Example 4 The procedure described in Example 3 was repeated replacing the Z-ethylhexanol by 577 grams (3.1 mols) of lauryl alcohol. The trilauryl phosphite was obtained in a yield of 97% based on the triphenyl phosphite starting material. The trilauryl phosphite was recovered from the reaction pot after removal of the phenol and other low boilers. The theoretical amount of pure phenol was recovered.

In a comparison example, when 3.1 mols of lauryl alcohol were heated with 1 mol of triphenyl phosphite exactly as in Example 4, except for the omission of the catalyst, and the mixture distilled through a fractionating column, a mixture of phenol and lauryl alcohol distilled.

The product left in the pot was a mixture of phenyldilauryl phosphite and diphenyl lauryl phosphite.

Example 5 1.0 gram of metallic sodium was added to 99.2 grams (3.1 mols) of methanol. Then 1 mol of triphenyl phosphite was added, the mixture allowed to stand for 20 minutes, and then the trimethyl phosphite was distilled at mm., leaving the phenol and dimethyl phenyl phosphite formed in the pot. The dimethylphenyl phosphite was subsequently recovered. The yield of trimethyl phosphite was 60% and the yield of dimethylphenyl phosphite 30% based on the triphenyl phosphite starting material.

Example 6 1.0 gram of sodium phenolate was added to 810 grams (3.0 mols) of stearyl alcohol. Then 1 mol of triphenyl phosphite was added, the mixture allowed to stand for 5 minutes, and the phenol formed distilled ofl at 10-20 mm. pressure. The tristearyl phosphite formed was recovered from the pot in a yield of 98% based on the triphenyl phosphite starting material.

From the yields obtained in the above examples, it can be seen that even with sodium alcoholate or sodium phenolate as a catalyst, the equilibrium is not 100% in the direction of the trialkyl phosphite, although it is substantially in that direction.

There can also be employed strong organic bases as catalysts. Typical of such bases are quaternary ammonium hydroxides, such as trimethyl benzyl ammonium hydroxide and substituted guanidines, such as pentamethyl guanidine, for example. The organic base can be employed in the same proportions as the metal alcoholates V and phenolates.

Strong inorganic bases such as sodium hydroxide and potassium hydroxide also are suitable and can be employed in the same amounts as the alcoholates and phenolates. However, weaker inorganic basic acting materials such as sodium carbonate are ineffective.

The catalyst should be a strong enough base to have a pH of at least 11 in a 0.1 N solution and preferably is an alkali metal alkoxide or phenoxide, as previously set forth.

We claim:

1. A process of preparing a trialiphatic hydrocarbon phosphite wherein the hydrocarbon group is selected from the group consisting of alkyl and alkenyl comprising transesterifying a triaryl phosphite with at least about 3 mols of a monohydroxy aliphatic hydrocarbon selected from the group consisting of alkanols and alkenols per mol of triaryl phosphite in the presence of a small but effective amount up to about 0.2 mol per mol of triaryl phosphite of an alkali metal alkoxide as a catalyst.

2. A process of preparing a trialiphatic hydrocarbon phosphite wherein the hydrocarbon group is selected from the group consisting of alkyl and alkenyl comprising transesterifying a triaryl phosphite with at least about 3 mols of a monohydroxy aliphatic hydrocarbon selected from the group consisting of alkanols and alkenols per mol of triaryl phosphite in the presence of a small but effective amount up to about 0.2 mol per mol of triaryl phosphite of an alkali metal phenate of a phenol selected from the group consisting of phenol and lower alkyl phenols as a catalyst.

3. A process of preparing a trialkyl phosphite comprising transesterifying a triaryl phosphite wherein the aryl group is selected from the group consisting of phenyl, chlorophenyl and phenyl having 1 to 3 lower alkyl substituents with at least about 3 mols of an alkanol per mol of triaryl phosphite in the presence of a small but efiective amount up to about 0.2 mol per mol of triaryl phosphite of an alkali metal alkoxide as a catalyst.

4. A proces of preparing a trialkyl phosphite comprising transesterifying a triaryl phosphite wherein the aryl group is selected from the group consisting of phenyl, chlorophenyl and phenyl having 1 to 3 lower alkyl substituents with at least about 3 mols of an alkanol per mol of triaryl phosphite in the presence of a small but efiective amount up to about 0.2 mol per mol of triaryl phosphite of an alkali metal phenate of a phenol selected from the group consisting of phenol and lower alkyl phenols as a catalyst.

5. A process according to claim 3 wherein the triaryl phosphite is triphenyl phosphite.

6. A process according to claim 4 wherein the triaryl phosphite is triphenyl phosphite.

7. A process of preparing a trialkenyl phosphite comprising transesterifying a triaryl phosphite wherein the aryl group is selected from the group consisting of phenyl, chlorophenyl and phenyl having 1 to 3 lower alkyl substituents with at least about 3 mols of an alkenol per mol of triaryl phosphite in the presence of a small but effective amount up to about 0.2 mol per mol of triaryl phosphite of an alkali metal alkoxide as a catalyst.

8. A proces of preparing a trialkenyl phosphite comprising transesterifying a triaryl phosphite wherein the aryl group is selected from the group consisting of phenyl, chlorophenyl and phenyl having 1 to 3 lower alkyl substituents with at least about 3 mols of an alkenol per mol of triaryl phosphite in the presence of a small but effective amount up to about 0.2 mol per mol of triaryl phosphite of an alkali metal phenate of a phenol selected from the group consisting of phenol and lower alkyl phenols as a catalyst.

9. A process according to claim 7 wherein the triaryl phosphite is triphenyl phosphite.

10. A process according to claim 8 wherein the triaryl phosphite is triphenyl phosphite.

11. A process of preparing a trialkyl phosphite comprising transesterifying triphenyl phosphite with at least about 3 mols of an alkanol per mol of triphenyl phosphite having 8 to 18 carbon atoms in the presence of a small but efiective amount up to about 0.2 mol per mol of triphenyl phosphite of the sodium salt of the alkanol as a catalyst.

12. A process of preparing a trialkyl phosphite comprising transesterifying triphenyl phosphite with at least about 3 mols of an alkanol per mol of triphenyl phosphite having 8 to 18 carbon atoms in the presence of a small but effective amount up to about 0.2 mol per mol of triphenyl phosphite of sodium phenate as a catalyst.

13. A process according to claim 7 wherein the alkenol is allyl alcohol.

14. A process according to claim 13 wherein the triaryl phosphite is triphenyl phosphite.

15. A process according to claim 8 wherein the alkenol is allyl alcohol.

16. A process according to claim 15 wherein the triaryl phosphite is triphenyl phosphite.

17. A process of preparing a trialiphatic hydrocarbon phosphite wherein the hydrocarbon group is selected from the group consisting of alkyl and alkenyl comprising transesterifying a triaryl phosphite wherein the aryl group is selected from the group consisting of phenyl, chlorophenyl and phenyl having 1 to 3 lower alkyl substituents with at least about 3 mols of a monohydroxy aliphatic hydrocarbon selected from the group consisting of alkanols and alkenols per mol of triaryl phosphite in the presence of a small but effective amount up to about 0.2 mol per mol of triphenyl phosphite of a basic material capable of having a pH of at least 11 in a 0.1 N solution.

18. A process of preparing a trialiphatic hydrocarbon phosphite wherein the hydrocarbon group is selected from the group consisting of alkyl and alkenyl comprising transesterifying a triaryl phosphite wherein the aryl group is selected from the group consisting of phenyl, chlorophenyl and phenyl having 1 to 3 lower alkyl substituents with at least about 3 mols of monohydroxy aliphatic hydrocarbon selected from the group consisting of alkanois and alkenols per mol of triaryl phosphite in the presence of a small but effective amount of a catalyst selected from the group consisting of a metal salt of a member of the group consisting of alkanols, alkenols, phenol and lower alkyl substituted phenols, said catalyst being a sufficiently strong base to have a pH of at least 11 in a 0.1 N solution.

19. A process of preparing a trialkyl phosphite comprising transesterifying a triaryl phosphite wherein the aryl group is selected from the group consisting of phenyl, cresyl and xylenyl with about 3 mols of alkanol per mol of triaryl phosphite in the presence of a small but effective amount of alkali metal alkoxide catalyst.

20. A process of preparing trimethyl phosphite comprising transesterifying a triaryl phosphite wherein the aryl group is selected from the group consisting of phenyl, chlorophenyl and phenyl having 1 to 3 lower alkyl substituents with at least about 3 moles of methanol per mole of triaryl phosphite in the presence of a small but efiective amount of a basic material capable of having a pH of at least 11 in a 0.1 N solution.

21. A process of preparing trimethyl phosphite which comprises transesterifying triphenyl phosphite with at least about 3 moles of methyl alcohol per mole of triphenyl phosphite in the presence of a small but effective amount of a basic material capable of having a pH of at least 11 in a 0.1 N solution.

22. A process of preparing trimethyl phosphite which comprises transesterifying triphenyl phosphite with at least about 3 moles of methyl alcohol per mole of triphenyl phosphite in the presence of a small but effective amount of sodium methylate as a catalyst.

References Cited in the file of this patent Milobendzki et al.: Chem. Polsk. 15, 66 (1917).

Milobendzki et al.: Chem. Abst, vol. 13, page 2867 (1919).

Ruggenberg et al.: J. Am. Chem. Soc. 70, 1802-3 (1948).

Kosolapofi: Organophosphorus Compounds, John Wiley & Sons, NY. (1951), page 191.

Groggins: Unite Processes in Organic Synthesis, 4th edition, McGraw-Hill Book (30., New York (1952), pages 616-619.

Landauer et al.: J. Chem. Soc., pages 2224-2234 (1953). 

18. A PROCESS OF PREPARING A TRIALIPHATIC HYDROCARBON PHOSPHITE WHEREIN THE HYDROCARBON GROUP IS SELECTED FROM THE GROUP CONSISTING OF ALKYL AND ALKENYL COMPRISING TRANSESTERIFYING A TRIARYL PHOSPHILTE WHEREIN THE ARYL GROUP IS SELECTED FROM THE GROUP CONSISTING OF PHENYL, CHLOROPHENYL AND PHENYL HAVING 1 TO 3 LOWER ALKYL SUBSTITUENTS WITH AT LEAST ABOUT 3 MOLS OF MONOHYDROXY ALIPHATIC HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF ALKANOLS AND ALKENOLS PER MOL OF TRIARYL PHOSPHITE IN THE PRESENCE OF A SMALL BUT EFFECTIVE AMOUNT OF A CATALYST SELECTED FROM THE GROUP CONSISTING OF A METAL SALT OF A MEMBER OF THE GROUP CONSISTING OF ALKANOLS, ALKENOLS, PHENOL AND LOWER ALKYL SUBSTITUTED PHENOLS, SAID CATALYST BEING A SUFFICIENTLY STRONG BASE TO HAVE A PH OF AT LEAST 11 IN A 0.1 N SOLUTION. 